A duck, some Newtons, and other fun stuff

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Homework Help Overview

The problem involves a duck with a specified mass and forces acting on it as it paddles through water. The forces include one directed due east and another at an angle south of east. The objective is to determine the magnitude and direction of the duck's displacement over a given time period while these forces are applied.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss calculating the net force acting on the duck and applying Newton's second law. There are attempts to resolve the components of the forces and subsequent calculations of acceleration. Some participants express confusion regarding the correct approach to finding the angle of displacement.

Discussion Status

The discussion includes various attempts to calculate the forces and accelerations, with some participants providing partial calculations. There is an indication that guidance has been offered regarding focusing on displacement rather than the angle of acceleration. Multiple interpretations of the problem are being explored, particularly concerning the correct method for determining displacement.

Contextual Notes

Participants note the urgency of the problem due to a deadline, which may influence the depth of exploration and reasoning. There is also a mention of potential confusion regarding the direction of forces and their components.

CelesteSeven
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A duck has a mass of 2.9 kg. As the duck paddles, a force of 0.11 N acts on it in a direction due east. In addition, the current of the water exerts a force of 0.19 N in a direction of 57° south of east. When these forces begin to act, the velocity of the duck is 0.13 m/s in a direction due east. Find the magnitude and direction (relative to due east) of the displacement that the duck undergoes in 2.0 s while the forces are acting.

What I need are the
magnitude m
direction ° south of east

I've tried drawing free body diagrams, but seem to get stuck. I'm not quite sure how to tell where the duck will be and how to find that in degrees. This is due at 11:30 tonight EST any any guidence would be greatly appreciated!
 
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The first step is to find the net force on the duck. Then apply Newton's 2nd law.
 
I've done this thus far:

Rx = .19(cos 57) +.11(cos0) = .21348N
Ry = .19(sin 57) + .11 (sin 0) = .1593N
Ax = .21348/2.9 = .07361 Ay = .1593/2.9 = .0549

then I do the tan-1 (.0549/.07361) which yields the wrong answer.

Any suggestions?
 
CelesteSeven said:
I've done this thus far:

Rx = .19(cos 57) +.11(cos0) = .21348N
Ry = .19(sin 57) + .11 (sin 0) = .1593N
OK. (But realize that the 0.19 N force is south of east.)
Ax = .21348/2.9 = .07361 Ay = .1593/2.9 = .0549

then I do the tan-1 (.0549/.07361) which yields the wrong answer.
You don't need the angle that the acceleration makes, you need the displacement. Find the change in the velocity in each direction and use it to find the displacement from the initial position. Then worry about finding the angle.
 

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